I use glass typically 1/4 inch thick with the following firing schedule:

From room temperature to 800F at 300 degrees per hour, hold for 10
minutes
From 800F to 1220F degrees at 400 degrees per hour, hold for 10 minutes
From 1220F to 1350F degrees at 600 degrees per hour, hold for 10 minutes
From 1350F to 960F degrees quickly “9999″, hold for 30 minutes
From 960F to 700F at 150 degrees per hour, no hold
Natural cooling to room temperature
Please adjust hold times for the size of your project. Remember this is
only a guide.